Platform for offshore installation

ABSTRACT

A method to manufacture a platform for offshore installation by determining one or more properties selected from a group consisting of a desired length, a cargo tonnage requirement, a heavy lift capacity, total buoyancy, and an operating depth of the platform, and designing a hull section, a first jack up rig, and a second jack up rig based on the determined properties. The first designed jack up rig is joined to a first end of the designed hull section, and the second designed jack up rig is joined to a second end of the designed hull section located opposite the first end.

FIELD OF THE DISCLOSURE

Embodiments disclosed herein relate generally to a platform for offshore installation, construction, and maintenance, and methods to manufacture the same.

BACKGROUND

Due to the high cost of increasing energy demand globally, more and more of the energy sector is looking to invest in renewable energy, such as wind turbines. Offshore wind turbines present unique challenges in construction and maintenance, especially as the energy output, and in effect, the size of the turbines steadily increase. The global offshore construction fleet is currently limited in not only the size and weight of the turbine in which they can install, but also the depth of water in which the turbine is installed.

Various regulatory frameworks around the world require that no merchandise shall be transported by water, or by land and water, on penalty of forfeiture of the merchandise, between points in the same country, including districts, territories, and possessions thereof embraced within the coastwise laws, either directly or via a foreign port, or for any part of the transportation, in any other vessel than a vessel built in and documented under the laws of the country and owned by persons who are citizens of the country, or vessels to which the privilege of engaging in the coastwise trade is extended.

Generally, in the United States, the Jones Act, which is part of the Merchant Marine Act, prohibits any foreign-built, foreign-owned or foreign-flagged vessel from engaging in coastwise trade within the United States.

Further, in the United States, the Jones act requires ships transporting cargo and/or equipment from a US port to a US port to be built in the US. This also applies to ships and vessels transporting cargo and equipment from US ports to US offshore installations.

Purpose built ships which are currently capable of offshore construction, installation, and maintenance operations are quite expensive and often purpose built for a narrow set of jobs. Additionally, the global fleet of used jack up rigs which are currently not seaworthy, or are seaworthy but not in use, is quite large. These already built jack up rigs may be retrofitted or reconditioned to make the rig seaworthy again, but are often undersized for today's scale of construction.

SUMMARY OF THE CLAIMED EMBODIMENTS

In one or more embodiments disclosed herein relate to a platform for offshore installation. The platform having two or more jack up rigs and a hull section, wherein the two or more jack up rigs are fixed to a first end and a second end of the hull section.

In another aspect, embodiments disclosed herein relate to a method to manufacture a platform for offshore installation by determining one or more properties selected from a group consisting of a desired length, a cargo tonnage requirement, a heavy lift capacity, total buoyancy, and an operating depth of the platform, and designing a hull section, a first jack up rig, and a second jack up rig based on the determined properties. The first designed jack up rig is joined to a first end of the designed hull section, and the second designed jack up rig is joined to a second end of the designed hull section located opposite the first end.

In another aspect, embodiments disclosed herein relate to a method of manufacturing a platform for offshore installation that complies with the Jones Act.

Other aspects and advantages will be apparent from the following description and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an elevation plan view of the platform according to embodiments disclosed herein.

FIG. 2 is a deck layout plan view of the platform according to embodiments disclosed herein.

DETAILED DESCRIPTION

In some embodiments, an offshore platform may include a hull section and two or more jack up rigs. Jack up rigs used may be newly constructed, or may be decommissioned and/or refurbished rigs. Jack up rigs are so named because they are self-elevating with movable legs that can be extended (“jacked”) above or below the hull. In some embodiments, at least one leg is provided. In other embodiments, the number of legs may be two, three, four, six or any number which may provide stability to the platform. Additionally, the number of jack up rigs included on the platform may be two, three, or more. One of ordinary skill in the art will be able to determine the number of jack up rigs depending on the desired characteristics and operating conditions of the platform.

Ports around the world have an excess of un-used jack up rigs which may be ready made for use in construction of the platform described herein. Using such already built jack up rigs may increase the speed of construction of the finished platform as well as lowering the overall costs of construction.

The movable legs of the jack up rig provide the capability of raising or lowering the rig over the surface of the sea. The movable legs may be designed to penetrate the sea bed, may be fitted with enlarged sections or footings, or may be attached to a bottom mat. The rig may be raised to a desired elevation above a sea surface by extending the movable legs, such that the legs will extend into the sea bed and the legs will support the rig.

In some embodiments, jack up rigs may be used as exploratory drilling platforms, for offshore operations, and wind farm service or installation platforms. When the tug or heavy lift ship moving the jack up rig reaches the work site, the crew of the rig extends the legs downward through the water and into the sea floor. In other embodiments, the crew may extend the legs downward through the water and onto the sea floor with mat supported jack ups. By extending the legs into or onto the sea floor, the jack up rig is anchored to the seafloor. Furthermore, the legs may be extended such that the rig is raised just above the surface of the sea, enabling the rig to be utilized to install equipment or to support operations. These types of jack up rigs may be used as part of the platform, according to one or more embodiments disclosed herein.

In some embodiments, a first jack up rig may include one or more extendable legs, one or more light duty cranes, and one or more heavy duty cranes. In some embodiments, a second jack up rig may include one or more extendable legs, one or more light duty cranes, and a helideck. In other embodiments, the first and second jack up rigs may be identical or different. In some embodiments, more than two jack up rigs may be used. One of ordinary skill in the art would be able to design and select the desired equipment for each jack up rig based on the properties and operating conditions of jack up rig or the platform.

In some embodiments, the hull section may include multiple-deck segments. Each multiple-deck segment may be known as a block and the blocks are put together, i.e., “block construction.” In some modern shipyards many components may be pre-installed on the blocks. In some embodiments, the components include equipment, pipes, electrical cables, and any other components which will be utilized within the designated block. The pre-installations may minimize the effort needed to assemble or install components within the hull on other blocks, once the blocks are welded together. In some embodiments, one or more of the multiple-deck segments may contain one or more buoyancy chambers, one or more ballast chambers, a cargo deck, living accommodations, and other equipment necessary for operations at sea. Several multi-deck segments may be combined to form the completed hull. Additionally, the hull may provide the buoyancy requirement of the platform and any cargo loaded that may be loaded thereon. In some embodiments, the jack up rigs may be self-buoyant, thereby reducing the buoyancy requirement of the hull section.

Modern ships and hulls may be produced of welded steel sheets. In some embodiments, specialized steels such as ABS steels having good properties for ship construction may also be used. In some embodiments, a variety of grades of steel may be used, such as those with higher or lower carbon content, as well as ABS steels, steel alloys. Additionally, different sections of the hull may be manufactured using different steels and materials based on the sections operating conditions. One of ordinary skill in the art would design and manufacture the different sections of the hull based on the desired properties of the hull.

In some embodiments, a desired toughness and ductility of the materials may be desired and will impact the selection of the type of steel or steel alloy to use. As used herein, toughness is a materials ability to withstand bending before fractures occur. Ductility refers to the ability of the material to deform before failure and may be dependent on temperature and typically decreases with a rise in temperature. A closely related term is notch ductility which is a measure of the relative toughness of steel measured by an impact test.

Referring now FIG. 1 and FIG. 2, an example of a platform 100 according to embodiments disclosed herein, where like numbers represent like parts.

In some embodiments, one or more jack up rigs 1 may be used for the platform 100. The jack up rigs 1 may have two or more legs 3. As shown, a first jack up rig may have two legs and a second jack up rig may have three legs. One of ordinary skill in the art will determine the number of legs based on the desired offshore installation. The legs 3 of each jack up rig may be a length suitable for the desired offshore installation, the site work depth, or have a wide range of operating depths. In some embodiments, the length of the legs 3 may be in the range of 5 to 200 meters, 10 to 180 meters, 15 to 170 meters, or 20 to 150 meters. The legs 3 of the jack up rigs 1 are designed to be lowered to the seafloor such that the platform 100 may become stable at the top of the leg and at sea level. In one or more embodiments, one or more extension pylons (not illustrated) may be located on top of the legs 3. The extension pylons may be used to raise the platform 100 above the top of the legs 3 to a desired working height above the sea level.

As described above, the jack up rigs 1 may be equipped, or fitted during platform fabrication, with one or more light duty cranes 4 having a lift capacity of up to 200 tons. Such light duty cranes may be used for general construction and offshore support operations such as onloading or offloading cargo. Additionally, one or more heavy lift cranes 5 may be equipped, or fitted on the jack up rigs 1, where the heavy lift cranes 5 may have a lift capacity up to or exceeding 1500 tons, for example. The heavy lift cranes 5 may be used for the full construction requirements of the offshore installation. In one or more embodiments, the light duty cranes 4 and heavy lift cranes 5 may be located on the deck space 6 of the platform 100, and may be attached to the deck space 6 by bolts and flanges, welds, or any other securing method as necessary to ensure the crane remain upright on the platform.

The platform 100 may have sufficient deck space 6 such that equipment for the operation of the platform may be installed offshore and the platform transported to the location of the operation. Pre-installing may prevent damage from occurring to the equipment by repeated loading and offloading by either the light duty crane or the heavy lift crane.

The platform 100 may also contain one or more propellers 10 on the underside of the platform 100. The propellers 10 may provide a part of, or the entirety of, the propulsion, heading control (e.g., steering) and transportation requirements of the platform 100. Propellers 10 may also be used for positioning of the platform 100 at the offshore site. For example, the propellers 10 may be used to transport the platform 100 to the offshore site, and then maintain the desired position while the jack up legs are lowered to the seafloor. In some embodiments, the propellers may be retractable and/or steerable. A position or height of the propellers may be adjustable, such that the propellers may be lifted above the underside of the platform for clearance in shallow draft ports or areas of operation, for example. The position of the propellers may also be rotatable (steerable), such that the propellers can direct their thrust in any direction so as to accomplish a desired heading control.

The jack up rigs 4 may be obtained from a number of sources. For example, the jack up rigs may be newly built jack up rigs, decommissioned jack up rigs, or refurbished jack up rigs. For each jack up rig, a ship yard in the desired country, for example the United States, may be used to build or refurbish it. For example, a jack up rig may be built from scratch in a shipyard or dry dock, or an existing jack up rig may be adapted for use with the pre-fabricated hull section or refurbished entirely, based on the condition of the jack up rig being used. Further, each jack up rig may be independently selected such that one jack up rig may be newly built and another jack up rig may be refurbished, for example. One of ordinary skill in the art would appreciate that any combination of sources for jack up rigs may be used without deviating from the envisioned method of manufacturing.

One or more embodiments disclosed herein relate to a method of manufacturing a platform, having a hull and one or more jack up rigs, for offshore installation and maintenance that solves the problem of various regulatory frameworks around the world, such as the Jones Act in the United States. According to one or more embodiments disclosed herein, a platform for offshore installation or operations may be manufactured by determining one or more of a desired length, a cargo tonnage requirement, a heavy lift capacity, total buoyancy, and an operating depth of the platform. Based on the determined properties, a hull section, a first jack up rig, and a second jack up rig are designed or selected. Additionally, more than two jack up rigs may be used and the hull selected accordingly, based on the determined properties. The first and second jack up rigs are joined to a first end and a second end of the hull section, respectively. In some embodiments, the second end is located opposite the first end. In one or more embodiments, the hull is water tight and designed such that the hull may provide sufficient buoyancy for the attached jack up rigs. In other embodiments one or more jack up rigs may be self-buoyant, thereby reducing the buoyancy requirement of the hull. Additionally, in one or more embodiments, the jack up rigs may be retrofitted or reconditioned for use in the platform. In some embodiments, the hull is retrofitted or reconditioned for use. Further, one of ordinary skill in the art would appreciate that the hull and one or more of the jack up rigs may be reconditioned or retrofitted for use in the platform.

Such a platform may be able to support the installation and maintenance of a variety of offshore projects. Such offshore projects may include wind turbine installations, oil rig support and maintenance, and production facilities (e.g., a mobile offshore production unit MOPU), among others. Additionally, the platform may be manufactured in such a way as to operate in a range of depths, such as depths ranging from 5 to 180 meters or more.

In one or more embodiments disclosed herein is a method to manufacture the platform for offshore operations. Accordingly, two or more jack up rigs 1 are selected based on the determined properties. A hull section 2 having a first end 7, a second end 8 located opposite the first end, the hull section located between the first end and the second end is also selected based on the determined properties, as described above, and attached between the two or more jack up rigs 1. The first of the two or more jack up rigs 1 is joined to the first end 7 of the hull section 2 and the second of the two or more jack up rigs 1 is joined to the second end 8 of the hull section 2. In this fashion, a floating platform 100 may be manufactured. In one or more embodiments, the two or more jack up rigs 1 may be joined so that the rigs are symmetrical across centerline 101. In one or more embodiments the two or more jack up rigs 1 may be joined so that the rigs are rotated with respect to each other by 45, 60, 90, 120, or 180° with respect to each other. Further, the rigs may be rotated with respect to each other by any regular or irregular angles. One of ordinary skill in the art would be able to select the jack up rigs, the hull section, and the arrangement of the three based on the determined properties.

To design the hull section, it may be necessary to determine one or more of a desired length and width of the finished platform, cargo tonnage requirements of the platform, heavy lift capacity of cranes, and operating depth of the platform. Further, it may be necessary to determine the total buoyancy requirement of the platform and cargo when selecting the hull section Similarly, more than two jack up rigs may be selected based on the platform requirements and the hull selected accordingly. The two or more jack up rigs and the hull section may be joined together by a bolted connection using a flange, or flanges, a welded connection, or combination thereof. One of ordinary skill in the art may be able to select the method of joining based on the jack up rig arrangement, hull section arrangement, materials of construction, and offshore requirements. Using the flange type connections, jack up rigs may be removed and replaced relatively easily if repairs are required or if the requirements of the platform change.

Referring again to FIGS. 1 and 2, an example of a platform 100 manufactured by the method described herein will now be described. As described below, the platform is manufactured for installation of wind turbines. However, one of ordinary skill in the art would appreciate that the platform may be manufactured for any number of purposes such as oil field exploration, oil and gas production, drilling, oil rig support, various offshore installation projects, and offshore maintenance.

As illustrated, two three-leg jack up rigs 1 are connected to the first end 7 and the second end 8 of the fabricated hull section 2. The hull section 2 and jack up rigs 1 form a stable platform 100 in which various components for offshore wind turbine installation may be loaded for transportation to the offshore installation site. As seen in FIGS. 1 and 2, wind turbine blades 20, wind turbine nacelles 22, and transition piece towers 24, among others, are loaded on the cargo deck 6 of the platform 100. Additionally, platform 100 may be provided with a helideck 26 which may be used for transporting people from the platform to shore during the time when the platform is stationary at the offshore site. Although not illustrated, embodiments herein may also include an elevating personnel platform for transfer to and from vessels and to and from a wind turbine tower (such as an installed wind turbine tower or one being installed, such as for attachment or maintenance of the turbine blades and other components).

Further, a multiplicity of light duty cranes 4 and at least one heavy lift crane 5 are located on the deck 6 of the platform 100. Using this arrangement, wind turbines may be installed offshore using the platform described herein without the need for multiple loading and offloading between two or more ships and platforms.

In some embodiments, where a three-leg jack up rig is used, one or more of the totality of legs may be removed, so that the total remaining legs is less than the original sum.

Additionally, the platform according to one or more embodiments herein, may be useful for installing wind turbines in a variety of sea depths. For example, the jack up rigs may be capable of installing wind turbines in as little at 5 meters of sea depth, or as much as 200 meters of sea depth. Additionally, extensions pylons (not illustrated) may be used on top of the platform which may pull the platform above the water for servicing and installing next generation wind turbines which may exceed 200 meters in height. These operating conditions and installation requirements are currently not possible to achieve with today's purpose built offshore installation ships.

Advantageously, a platform manufactured by the method described above may be useful for a wide range of operating depths and may be easily switched between installing 2-3 MW wind turbines and 9+ MW wind turbines. Additionally, the platform using existing, or newly built, jack up rigs where the hull section is designed and attached the jack up rigs in the necessary country to comply with regulatory framework. For example, in the United States such a construction may solve the Jones Act problem as a US produced platform is now able to transport equipment from a US port to a US offshore installation. This platform may also eliminate the need to use multiple ships and perform multiple loading and offloading operations, thereby reducing the likelihood of equipment damage during transportation and installation. Such a ship may also be used worldwide as the platform is self-sufficient for loading, transport, and installation.

While the disclosure includes a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments may be devised which do not depart from the scope of the present disclosure. Accordingly, the scope should be limited only by the attached claims. 

What is claimed:
 1. A platform for offshore installation comprising: two or more jack up rigs; a hull section, wherein the two or more jack up rigs are fixed to a first end and a second end located opposite the first end of the hull section.
 2. The platform of claim 1, wherein the first end and the second end of the hull section are joined to the two or more jack up rigs via bolts and flanges, welds, or combination thereof.
 3. The platform of claim 1, wherein the two or more jack up rigs each have two or more legs of a length of 5 to 200 meters.
 4. The platform of claim 1, wherein the two or more jack up rigs have been retrofitted or reconditioned for reuse.
 5. The platform of claim 1, wherein the hull has been retrofitted or reconditioned for reuse.
 6. The platform of claim 1, wherein the two or more jack up rigs each have two or more legs of a length of 10 to 180 meters.
 7. The platform of claim 1, wherein the hull comprises one or more materials selected from the group consisting of welded steel sheets, ABS steel, a steel having a high carbon content, a steel having a low carbon content, and one or more steel alloys.
 8. The platform of claim 1, further comprising: one or more cranes having a lift capacity up to 200 tons; one or more heavy lift cranes having a lift capacity up to or exceeding 1500 tons; and one or more retractable and steerable propellers.
 9. A method to manufacture a platform for offshore installation, the method comprising: determining one or more properties selected from a group consisting of a desired length, a cargo tonnage requirement, a heavy lift capacity, total buoyancy, and an operating depth of the platform; designing a hull section, a first jack up rig, and a second jack up rig based on the determined properties; joining the first designed jack up rig to a first end of the designed hull section; and joining the second designed jack up rig to a second end of the designed hull section, the second end located opposite the first end.
 10. The method of claim 9, wherein designing the first and second jack up rigs comprises independently selecting a newly built jack up rig, a decommissioned jack up rig, or a refurbished jack up rig.
 11. The method of claim 9, wherein joining the first jack up rig and joining the second jack up rig to comprises one or more flanges and bolts, welding, or a combination thereof.
 12. The method of claim 9, further comprising: attaching one or more of light duty cranes, heavy lift cranes, a helideck, living accommodations, cargo deck space, propellers, buoyancy chambers, ballast chambers, and extendable legs to the platform. 